Valve mechanism comprising a variable cross-section of a valve opening

ABSTRACT

The invention relates to a valve mechanism with a variable valve opening cross section, in which the valve mechanism is disposed at an admission opening of an internal combustion engine and has a gas exchange valve, which is acted on by the force of a valve spring and is displaceable axially back and forth inside a guide by a valve control unit; the position of the sealing slide relative to the gas exchange valve in the axial direction is continuously variable by means of an adjusting unit.  
     It is provided that a sealing slide ( 10 ) is disposed coaxially to the gas exchange valve ( 12 ), is acted upon by the force of a coupling spring ( 24 ), and is displaceable axially back and forth by the valve control unit.

[0001] The invention relates to a valve mechanism with a variable valveopening cross section having the characteristics recited in the preambleto claim 1.

PRIOR ART

[0002] It is known to use internal combustion engines as driving enginefor motor vehicles. In them, a fuel-air mixture is compressed andignited in the work chamber. The energy produced is converted intomechanical work. It is known for air or the fuel-air mixture to bedelivered to the work chamber via valves (inlet valves), and for theproducts of combustion to be removed from the work chamber via valves(outlet valves). For determining the efficiency of the engine,controlling these valves is of great significance. In particular, thegas exchange in the work chamber is controlled by way of controlling thevalves.

[0003] In addition to camshaft control, it is also known to employ anelectrohydraulic valve control. Electrohydraulic valve control offersthe capability of variable or fully variable valve control, making itpossible to optimize the gas exchange and thus to enhance the motorefficiency of the engine.

[0004] The electrohydraulic valve control includes a hydraulicallyactuatable control valve, whose control valve piston actuates a valvebody of the inlet and outlet valves and leads to a valve seat (valveseat ring) (closure of the valve) or moves away from it (opening of thevalve). The control valve can be actuated via a pressure control of ahydraulic medium. The pressure control is effected here via magnetvalves incorporated into the hydraulic circuit. To achieve the mostoptimal possible gas exchanges, the highest possible switching speeds ofthe control valve are needed. As a result of these high switchingspeeds, the valve body of the inlet and outlet valves strikes the valveseat ring at high speed. The result is on the one hand noise, and on theother, the partners in the valve suffer relatively high wear.

[0005] European Patent Disclosure EP 0 455 761 B1, for instance, has ahydraulic valve control device for an internal combustion engine as itssubject. The fundamental technological principle of this embodiment isto displace a motor valve by means of a controlled pressure of ahydraulic fluid. In this embodiment, it is provided that an electroniccontrol unit triggers a magnet valve, which in turn controls the motionof a storage piston, by way of which the stroke of the motor valve isvaried.

[0006] European Patent Disclosure EP 0 512 698 A1 describes anadjustable valve system for an internal combustion engine. Thisembodiment is one example of mechanical valve control via cams of arotating camshaft.

[0007] U.S. Pat. No. 4,777,915 has an electromagnetic valve controlsystem for an internal combustion engine as its subject. A similarembodiment of an electromagnetic valve control is known from EP 0 471614 A1. In these embodiments, the valve is moved back and forth todifferent positions by electromagnetic force. The electromagnets aredisposed inside a housing part of the cylinder head, in two differentregions. By the alternating activation of the electromagnets, the valveis moved alternatingly into two terminal positions, corresponding to theopening and closing positions of the valve, respectively. In theseterminal positions of the valve, the admission opening to the combustionchamber of the fuel-air mixture is then opened to the widest extent orcompletely closed.

[0008] Another embodiment is known from EP 0 551 271 B1. This embodimentinvolves a valve mechanism with a plate valve, which is disposed in apassage of an internal combustion engine. The fundamental principle ofthis embodiment is that the valve plate is divided in two; one half ofthe valve plate executes only a fraction of the stroke executed by theother half of the valve plate.

[0009] In these known embodiments for valve control, the major effort ofproduction and assembly of the valve mechanism, because of itscomplicated design, is especially disadvantageous. This adverselyaffects the costs for production and assembly. Moreover, in theseembodiments, extremely high speeds and strong forces for valve controlare necessary, so that an increased vulnerability to malfunction of thevalve control from major wear of the parts of the valve mechanism isunavoidable.

ADVANTAGES OF THE INVENTION

[0010] The valve mechanism of the invention having the definitivecharacteristics of the main claim offers the advantage over the priorart of creating a variable valve opening cross section by simple means.Because a sealing slide is disposed coaxially to the gas exchange valve,is acted upon by the force of a coupling spring, and is displaceableaxially back and forth by the valve control unit, and preferably theposition of the sealing slide relative to the gas exchange valve iscontinuously variable in the axial direction by a valve control unit, avalve mechanism is created which has a simple design and which functionsreliably and durably. The advantage of the valve mechanism of theinvention is in particular that a variable valve opening cross sectioncan be created, and each individual valve can be regulated separately.With the valve mechanism of the invention, the variable valve openingcross section can advantageously be created without high speeds andwithout strong forces, so that the vulnerability of this valve mechanismto malfunction is very slight. The valve mechanism of the invention canbe produced and assembled economically, because of its simple design.The invention advantageously creates a variable valve control by whichoptimization of the gas exchange and thus an increase in motorefficiency of the engine is possible.

[0011] In a preferred feature of the invention, it is provided that thevalve control unit is a camshaft.

[0012] In a further preferred feature of the invention, it is providedthat the gas exchange valve has a rotationally symmetrical basicconstruction and comprises a valve shaft, on whose lower end a valveplate is disposed.

[0013] In a further preferred feature of the invention, it is providedthat the valve plate has a conical circumferential face, which forms thesealing seat of the gas exchange valve.

[0014] Also in a preferred feature of the invention, it is provided thatin the closing position of the valve mechanism, the sealing seat of thegas exchange valve directly contacts both a sealing seat of the sealingslide and a valve seat ring of the cylinder head.

[0015] Moreover, in a preferred feature of the invention, it is providedthat the sealing slide comprises a bushlike bearing body, which isdisposed displaceably axially back and forth inside a guide of thecylinder head.

[0016] As a result of these advantageous features of the invention, thedelivery of the fuel-air mixture can be regulated with great precision,and a high efficiency of the engine can thus be achieved.

[0017] Further advantageous features of the invention will becomeapparent from the characteristics recited in the dependent claims.

[0018] Drawings

[0019] The invention will be described below in further detail in termsof an exemplary embodiment in conjunction with the associated drawings.Shown are:

[0020]FIG. 1, a section through a cylinder head with the valve mechanismof the invention; and

[0021]FIG. 2, a perspective view of a sealing slide of the valvemechanism of the invention.

DESCRIPTION OF THE EXEMPLARY EMBODIMENT

[0022] In both figures, the individual parts of the valve mechanism ofthe invention are shown schematically and only with those componentsessential to the invention. Identical parts of the valve mechanism ofthe invention are identified by the same reference numerals throughoutthe drawings and as a rule will each be described only once.

[0023] In FIG. 1, the valve mechanism of the invention is shown in itsdisposition in the cylinder head 18 of an internal combustion engine.The valve mechanism has a gas exchange valve 12, which is acted upon bythe force of a valve spring 16. The gas exchange valve 12 isdisplaceable axially back and forth inside a guide, and the displacementmotion is generated by a valve control unit. In a preferred feature ofthe invention, a camshaft (not shown) is provided as the valve controlunit.

[0024] The gas exchange valve 12 has a rotationally symmetrical basicconstruction and comprises a valve shaft 14, on the lower end of which avalve plate 20 is disposed. FIG. 1 shows the valve mechanism in theclosing position of the gas exchange valve 12. The sealing seat 28 ofthe gas exchange valve 12 is in direct contact with both a sealing seat30 of the sealing slide 10 and a valve seat ring 22 of the cylinder head18.

[0025] The structure and mode of operation of gas exchange valves 12 perse are well known, so that this need not be addressed in further detailin the context of the present description.

[0026] The invention provides that a sealing slide 10 is disposedcoaxially to the gas exchange valve 12. The sealing slide 10 is actedupon by the force of a coupling spring 24 and is displaceable axiallyback and forth. The displacement motion of the sealing slide 10 islikewise generated by the camshaft (not shown), by which thedisplacement motion of the gas exchange valve 12 is controlled.

[0027] In FIG. 2, the sealing slide 10 is shown schematically in aperspective view. The sealing slide 10 substantially comprises a bearingbody 40 and a sealing body 38. The bearing body 40 of the sealing slide10 is embodied in bushlike fashion and is disposed displaceably axiallyback and forth inside a guide of the cylinder head 18. On its lower end,the sealing slide 10 has a cylindrical sealing body 38, whose outer faceforms the sealing seat 30. The sealing body 38 is connected to thebearing body 40 via connecting rods 42.

[0028] A stop disk 26 is secured to the bearing body 40, near the lowerend thereof. To facilitate assembly, this stop disk 26 comprises twoparts. The two parts of the stop disk 26 are surrounded by a clampingring 36, by which they are held together.

[0029] The connection between the sealing body 38 and the bearing body40 is designed such that sufficient room remains for the air flowingthrough, or for the fuel-air mixture. As a result, for letting the airor the fuel-air mixture both in and out, there is advantageously a largeenough admission opening inside the sealing slide 10 to allow thismedium to flow through unhindered.

[0030] The valve mechanism shown in FIGS. 1 and 2 has the followingfunction:

[0031] By means of the valve control unit, which in a preferred featureof the invention is a camshaft (not shown), the gas exchange valve 12can either be opened or closed. The gas exchange valve 12 is presseddownward on the valve shaft 14 via the camshaft, as in a conventionalvalve drive, the course of motion of the gas exchange valve 12 is thuscontrolled. All known methods that are based on the principle of the cuptappet, tilt lever, drag lever, and the like, can be employed.

[0032] The camshaft 44 operates counter to the restoring force of thevalve spring 16 that is braced on the cylinder head 18 and on the valveplate 20 which moves jointly with the gas exchange valve 12. By rotationof the camshaft 44, the gas exchange valve 12 is pressed downward, andthe sealing seat 28 of the gas exchange valve 12 lifts away from thevalve seat ring 22.

[0033] Via the coupling spring 24, which is under a certain initialtension, the sealing slide 10 is moved in slaved fashion. The couplingspring 24 is braced on the valve plate 20 and on the stop disk 26, whichis connected to the sealing slide 10. As a result, the sealing seat 30of the sealing slide 10 is pressed against the sealing seat 28 of thegas exchange valve 12. Since an annular gap seal exists between thesealing body 38 and the valve seat ring 22, only a very slight airquantity (leakage) can reach the combustion chamber 32.

[0034] The gas exchange valve 12 and thus also the sealing slide 10follow the cam course, until the stop disk 26 strikes the control slide34.

[0035] The control slide 34 is adjustable in the axial direction of thevalve shaft 14 in its outset position relative to the gas exchange valve12. The adjustment can be done electrically, hydraulically, orpneumatically. The control slide 34 can be adjusted via a suitableadjusting unit (not shown). Otherwise, the position of the control slide34 inside the valve mechanism remains fixed, even if forces are exertedon it from outside. The adjusting units can each be actuatableelectrically, hydraulically, or pneumatically.

[0036] As soon as the stop disk 26 strikes the control slide 34, thesealing slide 10 can no longer execute any motion in the openingdirection of the gas exchange valve 12. Since the gas exchange valve 12is moved onward by the camshaft, the sealing seat 28 of the gas exchangevalve 12 lifts away from the sealing seat 30 of the sealing slide 10,and air can penetrate the combustion chamber 32. In the process, thecoupling spring 24 is compressed.

[0037] If the gas exchange valve 12 follows the closing flank of thecamshaft, it is pressed in the closing direction by the valve spring 16.The sealing seat 28 of the gas exchange valve 12 presses against thesealing seat 30 of the sealing slide 10. The sealing slide 10 is carriedalong, until the sealing seat 28 of the gas exchange valve 12 rests onthe valve seat ring 22, and the gas exchange valve 12 is closed.

[0038] The gas exchange valve 12 and thus also the sealing slide 10follow the cam course of the camshaft 44. At a certain instant, the stopdisk 26, which is connected to the sealing slide 10, strikes the controlslide 34 (in the state shown in FIG. 1). After that, the sealing slide10 can no longer follow the cam course of the camshaft 44. The gasexchange valve 12 lifts from the sealing slide 10, and air can get intothe combustion chamber.

[0039] By axial displacement of the position of the control slide 34 viaan adjusting unit (not shown), it can be established when the sealingseat 28 of the gas exchange valve 12 will lift from the sealing seat 30of the sealing slide 10. In this advantageous way, the opening crosssection of the gas exchange valve 12 and thus also the quantity of airreaching the combustion chamber 32 can be regulated.

1. A valve mechanism with a variable valve opening cross section, inwhich the valve mechanism is disposed at an admission opening of aninternal combustion engine and has a gas exchange valve, which is actedon by the force of a valve spring and is displaceable axially back andforth inside a guide by a valve control unit, characterized in that asealing slide (10) is disposed coaxially to the gas exchange valve (12),is acted upon by the force of a coupling spring (24), and isdisplaceable axially back and forth by the valve control unit.
 2. Thevalve mechanism of claim 1, characterized in that the position of thesealing slide (10) is continuously variable.
 3. The valve mechanism ofone of the foregoing claims, characterized in that the valve controlunit is preferably a camshaft.
 4. The valve mechanism of one of theforegoing claims, characterized in that the gas exchange valve (12) hasa rotationally symmetrical basic construction and comprises a valveshaft (14), on whose lower end a valve plate (20) is disposed.
 5. Thevalve mechanism of claim 4, characterized in that the valve plate (20)has a conical circumferential face, which forms the sealing seat (28) ofthe gas exchange valve (12).
 6. The valve mechanism of one of theforegoing claims, characterized in that in the closing position of thevalve mechanism, the sealing seat (28) of the gas exchange valve (12)directly contacts both a sealing seat (30) of the sealing slide (10) anda valve seat ring (22) of the cylinder head (18).
 7. The valve mechanismof one of the foregoing claims, characterized in that the sealing slide(10) comprises a bushlike bearing body (40), which is disposeddisplaceably axially back and forth inside a guide of the cylinder head(18).
 8. The valve mechanism of one of the foregoing claims,characterized in that the bushlike bearing body (40) of the sealingslide (10) forms the guide of the gas exchange valve (12), inside whichthe gas exchange valve (12) is displaceable axially back and forth. 9.The valve mechanism of one of the foregoing claims, characterized inthat the sealing slide (10), on its lower end, has a cylindrical sealingbody (38), whose outer face forms the sealing seat (30).
 10. The valvemechanism of one of the foregoing claims, characterized in that thesealing body (38) is connected to the bearing body (40) via connectingrods (42).
 11. The valve mechanism of one of the foregoing claims,characterized in that a stop disk (26) is secured to the bearing body(40) of the sealing slide, near its upper end.
 12. The valve mechanismof one of the foregoing claims, characterized in that the stop disk (26)comprises two parts.
 13. The valve mechanism of one of the foregoingclaims, characterized in that the two parts of the stop disk (26) aresurrounded by a clamping ring (36).